Оксидный поверхностный слой и твердофазная свариваемость титановых сплавов

Abstract

It is known that the ultrafine-grained (UFG) structure in alloys is thermally unstable. An important task for the modern aviation engineering is to preserve the UFG structure in parts for responsible purposes after their production in order to maintain the high level of their mechanical properties. In particular, the solution to this task necessitates the reduction of the temperature of solid-phase bonding while ensuring the necessary quality of the permanent joint. It is known that along with the average grain size, the oxide surface layer can also significantly affect the solid-phase weldability of titanium alloys at low temperatures, but the latter has been extremely poorly studied. In this regard, the influence of an oxide film is considered for domestic two-phase titanium alloys VT6 (Ti-Al-V system) and VT8 (Ti-Al-Mo system), which differ in the main alloying element for the stabilization of the β-phase. As a result of the experiments, the absence of an oxide layer in the zone of solid-phase connection of the ultrafine-grained (UFG) VT6 alloy after welding in vacuum at a reduced temperature of 600°C was metallographically revealed. This has a positive effect on the quality of welded samples according to the conducted mechanical tests. A continuous oxide layer was found in the solid-phase joint zone after welding at a temperature of 600°C for the UFG alloy VT8. The experimental results indicate that the UFG titanium alloy VT6, doped with relatively “mobile” vanadium, has the potential to reduce the lower temperature of solid-phase welding in vacuum by 50°C in comparison with the titanium alloy VT8.